Bulletin of the American Physical Society
2020 Fall Meeting of the APS Division of Nuclear Physics
Volume 65, Number 12
Thursday–Sunday, October 29–November 1 2020; Time Zone: Central Time, USA
Session MN: Instrumentation: Polarization, Spin, and Targets |
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Chair: Mark Dalton, Jefferson Lab |
Saturday, October 31, 2020 2:00PM - 2:12PM |
MN.00001: Polarized Source Setup and Helicity Correlated Beam Asymmetry Results for PREX-2 Sachinthani Premathilake Parity-violating electron scattering provides a clean probe of neutron densities that is model independent and free from most of the strong interaction uncertainties. The PREX-2 and CREX experiments that ran at Jefferson lab aimed to measure the nucleon skin thickness in 208Pb and 48Ca via parity violating electroweak asymmetry in the elastic scattering of longitudinally polarized electrons. One of the crucial systematic uncertainty that both of these experiments were sensitive to is the non-parity violating asymmetries that resulted from the helicity-correlated false asymmetries in the polarized electron beam. This talk will describe the polarized source setup and helicity-correlated beam asymmetry results for PREX-2. [Preview Abstract] |
Saturday, October 31, 2020 2:12PM - 2:24PM |
MN.00002: High Magnetic Field Polarization of $^3$He for High-Luminosity Scattering Targets James Maxwell Polarized $^3$He nuclear targets have been invaluable surrogates for polarized neutron targets in spin-dependent scattering studies of the quark and gluon structure of matter. Traditional polarized $^3$He targets have seen dramatic improvements in the last three decades, however increased wall relaxation at high magnetic fields limits their use in spectrometers that utilize high-magnetic-field tracking systems, such as Jefferson Lab's CLAS12 spectrometer. Developments in high-magnetic-field metastability exchange optical pumping of $^3$He, recently brought to bear for a polarized $^3$He ion source for RHIC and the EIC, offer a path to a high-field polarized $^3$He fixed target. By combining these new techniques with a double-cell cryogenic target design, such as the one used for the MIT-Bates 88-02 experiment, polarization and target density comparable to traditional polarized $^3$He targets can be reached while within a high magnetic field environment. We will discuss the conceptual design for such a target, share plans for its first application in a program of longitudinal polarized scattering in Jefferson Lab's Hall B, and show a concept for achieving polarization transverse to the incident beam with this method. [Preview Abstract] |
Saturday, October 31, 2020 2:24PM - 2:36PM |
MN.00003: The Polarized-Target System for the SpinQuest Experiment at Fermilab Zulkaida Akbar The SpinQuest experiment at Fermilab aims to measure the Sivers asymmetry for the $\bar{u}$ and $\bar{d}$ sea quarks in the range of 0.1 $< x_{B} <$ 0.5 using the Drell-Yan production of dimuon pairs. A nonzero Sivers asymmetry would provide an evidence for nonzero orbital angular momentum of the sea quarks. The proposed beam intensity is 1.5~$\times$~10$^{12}$ of 120 GeV unpolarized proton/sec. The experiment utilizes a target system consisting of a 5T superconducting magnet, transversely polarized NH$_3$ and ND$_3$ targets, a $^4$He evaporation refrigerator, a 140 GHz microwave source and a large pumping system. The expected average target polarization is 80$\%$ for the protons and 32$\%$ for the deuterons. The polarization will be measured with three NMR coils per target cell. A quench analysis and simulation in the superconducting magnet are performed to determine the maximum intensity of the proton beam before the magnet become resistive. A GEANT based simulation is used to calculate the heat deposited in the magnet and the subsequent cooling processes are modeled using the COMSOL Multiphysics. [Preview Abstract] |
Saturday, October 31, 2020 2:36PM - 2:48PM |
MN.00004: NMR Analysis of Polarized Spin-1 Solid-State Targets Joey Clement, Dustin Keller The spin-1 NMR lineshape for polycrystalline materials can be manipulated with selective semi-saturating RF. This process can be performed strategically during dynamic nuclear polarization to continuously enhance the tensor polarization of the spin-1 target. Our research offers new analytical descriptions of the spin polarized energy levels that produce the lineshape (as well as new analysis of the lineshape itself). A simulation of the spin-1 NMR lineshape's response to polarizing radiation as well as semi-saturating RF has been developed, with the aim of studying tensor polarization enhancement using the RF power and time profile with optimized modulation. Additional solid-state NMR effects are also included in the simulation, such as a treatment of the adiabatic-fast-passage (AFP). Both the analytical description of the information contained in the lineshape as well as the method to produce simulations of enhancement under the environment necessary for application in high-energy and nuclear scattering experiments are provided. [Preview Abstract] |
Saturday, October 31, 2020 2:48PM - 3:00PM |
MN.00005: Compton Polarimetry for the PREX-II Experiment Adam Zec The Jefferson Lab Continuous Electron Beam Accelerator Facility’s experimental Hall A employs a Compton polarimeter to measure incoming beam polarization for parity violating electron scattering experiments. The polarimeter operates by amplifying green laser light in a Fabry-Perot cavity which then Compton scatters off the incoming electron beam. The scattered photons are then passed through a scintillating GSO (Gadolinium Oxyorthosilicate) crystal with a single photomultiplier tube. The polarization measurement is conducted by taking advantage of the helicity-dependence of compton scattering. By measuring the integrated signal from photons scattered while the beam is in different helicity states, we generate a differential asymmetry between these states, which then yields information about the electron beam’s longitudinal polarization. Measuring the asymmetry requires a robust background subtraction of helicity-correlated asymmetry as well as identifying the compton edge from observing spectra. The beam polarization is an important component needed to determine the parity-violating asymmetry for the PREX-II experiment. This talk will focus on the analysis of the integrating photon detector data. [Preview Abstract] |
Saturday, October 31, 2020 3:00PM - 3:12PM |
MN.00006: Moller Polarimetry for the Neutron Skin Experiments at Jefferson Lab Donald Jones The two sister experiments PREX-2 and CREX have recently performed measurements of the neutron skin on Pb-208 and Ca-48 respectively via parity-violating electron scattering. The measured scattering asymmetries are normalized to the beam polarization making electron beam polarimetry central for precision determinations of the neutron skins. Furthermore, polarimetry was essential for minimizing and interpreting key systematics effects such as the transverse and null asymmetries. M\o ller polarimetry has been utilized in Hall A for two decades. However, the system has been upgraded since PREX-1 to utilize a foil target of pure iron magnetized out of plane along the direction of the beam, allowing for sub-1% precision on the beam polarization. Modifications were also made to the spectrometer to allow for the higher energies of the 12 GeV era at Jefferson Lab. During PREX-2 and CREX, the upgraded Hall A M\o ller polarimeter was first commissioned at low energy (1-2 GeV) and indeed delivered precision results. I will describe the M\o ller polarimetry data taken for these experiments, including some unexpected findings. [Preview Abstract] |
Saturday, October 31, 2020 3:12PM - 3:24PM |
MN.00007: Key Moller Polarimetry Systematics for the PREX-II/CREX Experiments Eric King Over the past few years the Moller polarimeter in Hall A has been upgraded to reduce systematic uncertainties related to target polarization and to allow operation at high energies \textgreater 10 GeV. The upgraded polarimeter was first commissioned and operated at low energy (1 GeV) for PREX-II creating a special set of challenges. Presented here is an outline of the upgraded polarimeter and a discussion of some of the challenges faced during PREX-II and CREX including reduction of key systematics related to the spectrometer optics. One key systematic uncertainty, the Levchuk effect which arises from broadening due to the Fermi motion of the inner unpolarized target electrons will be particularly addressed. [Preview Abstract] |
Saturday, October 31, 2020 3:24PM - 3:36PM |
MN.00008: Atomic Hydrogen Moller Polarimeter Design for P2 Experiment Yufan Chen, Rakitha Beminiwattha P2 experiment held by MESA in Mainz is targeting for a measurement of the weak charge of the proton based on the parity violating asymmetry in the elastic scattering of polarized electrons off unpolarized nuclei, it is proposed to get the weak mixing angle $\sin^2 \theta_\omega$ to a precision as high as of 0.13\% at a four momentum transfer of $Q^2=4.5*10^-3 GeV^2$ to test the standard model to a high mass scale at 155MeV beam energy. Therefore an atomic hydrogen M\o ller polarimeter is proposed for measuring beam polarimetry real time using M\o ller scattering. \par A magnetic chicane based design is proposed for detecting M\o ller electrons for the polarimeter. \par The polarimeter is designed to precisely separate the main beam and scattered M\o ller electrons while maintaining a total length of 1.72 meters and 0.5-0.75T for the dipole magnets. [Preview Abstract] |
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